Digital subscriber line (DSL) technologies can provide a large bandwidth for digital communications over existing subscriber lines. DSL systems may transmit and receive data over pairs of twisted copper wires. Examples of DSL technologies include those defined by standards including asymmetric DSL 2 (ADSL2); very-high-speed DSL (VDSL); very-high-speed DSL 2 (VDSL2); G.vector; and G. fast, which is a future standard to be issued by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Study Group 15 (SG15). These broadband access communication technologies may provide data for triple-play services, including television, Internet, and voice over Internet protocol (VOIP) phones. Because of the increasing use of such services, there is a need to increase data rates to meet user demands.
As data rates increase and the corresponding systems become more complex, other issues may arise. For example, when transmitting data over subscriber lines, crosstalk (XT) interference may occur between the transmitted signals over adjacent twisted-pair subscriber lines in a same or nearby bundle of lines. Crosstalk may generally refer to a signal on one wire or cable causing an undesired effect on another wire or cable. Near-end crosstalk (NEXT) may refer to crosstalk at the same end of the wire or cable as the transmitter. Far-end crosstalk (FEXT) may refer to crosstalk at the other end of the wire or cable as the transmitter. Crosstalk, including NEXT and FEXT, may limit the performance of various DSL systems. For example, although channel capacity in the physical media dependent (PMD) layer of a DSL system may be high (e.g., near gigabits in G.fast) with a single subscriber line, when multiple subscriber lines are deployed in a same binder, the actual data rate may be lower than the channel capacity due to NEXT and/or FEXT.